YES, IT'S nonsense, but the following list of words - 'Pad kid poured curd pulled cold' - is easy enough to read. Now try saying it out loud, then repeating it quickly, ten times in a row.

If you can pull that off without getting a single syllable wrong, you're a genius of rare eloquence, the Professor Henry Higgins of the modern age.

Researchers at the Massachusetts Institute of Technology in Boston - one of America's brainiest seats of learning, known as MIT - have declared this nonsense sentence the hardest tongue twister in history.

The new tongue twister is even harder to say than the previous claimant to the title: 'The seething sea ceaseth and thus the seething sea sufficeth us.' In 1990, this was the sentence declared by American word expert William Poundstone (a graduate of MIT, incidentally) to be the toughest ever.

Most good tongue-twisters like this one rely on alliteration and assonance - using words with similar letters or sounds - combined with tiny differences between those letters and sounds.

If the words in a sentence are identical-sounding, then it's usually fairly straightforward to pronounce. 'I scream, you scream, we all scream for ice cream' looks like tricky wordplay because of the different spellings of 'I scream' and 'ice cream'. But the sentence is, in fact, a doddle to repeat over and over, because the sounds are the same. The brain can also handle combinations of very different words. That's why one famous tongue-twister is actually rather easy to say: 'How much wood would a woodchuck chuck, if a woodchuck could chuck wood?'

It depends on the repetition of two extremely different words, 'wood' and 'chuck', that each never change sound during the whole of the sentence. But the brain gets much more befuddled by trying to make the tiny jump between two near-identical sounds; and it ends up confusing one sound with the other.

'She sells seashells on the seashore' twists the tongue because the 's' sound and 'sh' sound are similar but not identical. As a result, it's a lot trickier to repeat than a sentence of very different words like, say: 'She flogs umbrellas on the beach.'

Trivial as all this seems, the MIT team aren't just messing about. At the recent 166th meeting of the Acoustical Society of America in San Francisco, they were investigating the way our speech patterns work - or don't work.

What they've discovered is that different types of tongue twister have a different effect on our brains, lips, tongue and throat as we produce mistakes in our speech. Here are some of those different types - and the reasons why they make speech so impossibly difficult...

THE MEANINGLESS LIST OF WORDS

THIS is the category that the new, most difficult tongue twister in the world fell into - 'Pad kid poured curd pulled cold.'

There are simpler examples, too, like the best known of word-list tongue twisters, 'Red lorry, yellow lorry'.

The MIT researchers got their guinea pigs to say 'Top cop' over and over again, very quickly. The classic mistake here is to end up saying 'cop cop' instead.

Another tricky customer in this category is 'toy boat'. Say it enough times, and you're very likely to make the mistake of saying 'toy boyt' instead.

In both examples, our poor muddled brain can't cope with certain, sudden, quick differences in speech. And so it starts to create patterns that aren't there and ends up making a mistake.

With 'top cop', we tend to put the 'c' at the beginning of both words; with 'toy boat', we transfer the vowel sound 'oy' from the first syllable to the second.

The MIT experts also showed how we start to create a sort of halfway house between the two different letters, 't' and 'c'. With the 'top cop' example, some of the subjects of their academic study started to make a sort of 'tcop' sound, with the 't' and the 'c' said at almost the same time.

Other subjects inserted a vowel between the 't' and the 'c' to produce a kind of 'tah-cop' sound. The experts even have a name for the new mistaken words we create with these combined double letters at the beginning - they're called 'double onsets'.

FULL SENTENCE TONGUE TWISTERS

At LEAST these ones make sense - even though they render your speech nonsensical. Among them is the Guinness Record breaker for being the most difficult: 'The sixth sick sheik's sixth sheep's sick'. Saying that just once has your tongue in knots.

Then there are the classic ones we tend to remember from our childhood days, like the most famous tongue twister of all:

I can't repeat the classic mistake that usually emerges in this one - this is a family newspaper. But a similar rude effect can be produced with

'I slit the sheet, the sheet I slit;'And on the slitted sheet I sit.'

Needless to say, the MIT brainiacs didn't demean themselves with such vulgarities. What they did discover, however, is that the tongue twisters that are simply lists of words produce more of the 't'cop' type of mistake. Meanwhile, the full sentence tongue twisters produced more of those 'tah-cop' mistakes.

The MIT team haven't reached any formal conclusions about why we make these different mistakes. But they suggest one reason for the difference is the regular rhythm of the word lists - like 'red lorry, yellow lorry' - against the irregular rhythm of long sentences like the Peter Piper example.

LIP SHAKERS AND MOUTH TWISTERS

Try saying 'Peggy Babcock' over and over again - and you'll soon get in trouble. But why? Both words are pretty simple, and they're pretty easy to pronounce on their own.

"Tongue twisters tend to move between different bits of the mouth which we find hard to co-ordinate," says language expert Mark Forsyth, author of bestsellers The Etymologicon and The Elements Of Eloquence.

"So, with "Peggy Babcock", you make the "p" sound with your lips; the "g" comes from the back of the mouth; the "b" is again from the lips; the "k" is again from the back of the mouth. So we move back and forth, making the sounds in different places in our mouth, and we get in a muddle."

THE SPANISH QUESTION

When midfielder Steve McManaman moved to Real Madrid in 1999, Spanish football fans were delighted. Less so Spanish commentators.

'"N" and "m" sounds come through the nose," says Mark Forsyth. "The Spanish have trouble with nasal sounds, so McManaman's name was a nightmare. You can replicate the effect by saying his name while holding your nose. The "Steve" bit comes out fine; the "McManaman" bit isn't so easy."

We shouldn't get too smug about pronunciation, though. All languages have their strengths and weaknesses. So, the Xhosa tribes of south-eastern South Africa incorporate three main types of clicking sounds in their language that we English speakers couldn't hope to reproduce.

But you don't have to go that far to find unpronounceable sounds.

"The Germans use a particular fricative noise at the back of the throat," says Mark Forsyth. "You produce a fricative when you blow to make the sound - like when you say "f" or "s". The Germans use the fricative from the back of the throat for the "k" sound in "Bach", as in the composer Johann Sebastian Bach. The British are very bad at that fricative - except in Liverpool, where they use it a lot."

Safe to say, then, that Steve McManaman, born in Kirkdale, Liverpool, in 1972, won't have much trouble when it comes to pronouncing his German composers.

Harry Mount is the author of Amo, Amas, Amat And All That - How To Become A Latin Lover (Short Books).

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